Define upgrade path for ComponentConfig #1681
Description
kubeadm allow usage of component config for defining settings for kubelet and kube-proxy; component configs are stored in ConfigMaps and reused when joining nodes or doing upgrades.
However, as of today kubeadm does not yet define a procedure for upgrading component configs in the case such API change format e.g. change from kube-proxy/config/v1alpha1 to kube-proxy/config/v1alpha2.
As an initial step, we should evaluate if this is the scope of kubeadm because it requires a certain degree of coordination across nodes (there should not be old components referring to a new/not supported component config), and this can't be achieved by kubeadm alone.
If this is the case, it should be documented what is the expected procedure higher-level tools/user's should take care of.
It is also important to keep in mind nuances of component config management for kubelet (1CM per version, copied locally) and kube-proxy (1CM, linked by all instances).
k/e issue + KEP:
kubernetes/enhancements#1381
/cc @rosti